The Norwegian man who killed 77 people at a youth summer camp played World of Warcraft for almost seven hours a day for several months prior to the massacre.

However, new evidence suggests that violent video games cause those who play them to feel bad about the moral codes they break.

The recent study led by Mathew Grizzard, PhD, assistant professor in the University at Buffalo Department of Communication is one of several showing that video game players who commit immoral acts express feelings of guilt when committing them.

"We found that after a subject played a violent video game, they felt guilt and that guilt was associated with greater sensitivity toward the two particular domains they violated - those of care/harm and fairness/reciprocity," Grizzard said.

The study, titled as "Being Bad in a Video Game Can Make Us More Morally Sensitive," involved 185 subjects who played a violent shooter game as either a guilt-inducing terrorist character, or as a UN peacekeeper.

Even though the subjects performed the same actions regardless of their assigned character, players who played as a terrorist character exhibited significantly more guilt about the moral violations they made in the game.